The ancient remains of two teenage boys whose skulls were artificially deformed have been discovered in a Croatian burial pit. One of the boys was found to have had his skull lengthened using hard and rigid tools, while the other's skull had been compressed and heightened, likely with the use of bandages and tape.

Artificial cranial deformation (ACD) has been practiced by humans for thousands of years, with evidence going all the way back to the Neolithic period. It is found in cultures across the globe, from the ancient Maya to the Huns of Mongolia—and it was still being performed in some regions until very recently. Normally, skull shaping begins just after birth, when the bone is flexible.

"It is still not clear why this practice emerged," Mario Kovak, from the Institute for Anthropological Research in Zagreb, Croatia, told Newsweek. "it is possible that they used it as a marker of beauty/fashion, or as a visual indicator of association to a certain cultural group, or maybe as an indicator of social status."

Kovak, Ron Pinhasi of the University of Vienna and other colleagues have now published research into ACD being practiced in Croatia in the fourth and fifth centuries AD—a time when a great migration was taking place across Europe.

The remains of three teenage boys were found in a newly discovered pit at the Hermanov vinograd archaeological site, in Osijek—a region in the east of Croatia. Two of those individuals—known as SU 259 and SU 750—were found to have had their heads artificially deformed. Images show how the skulls had been elongated, flattened and heightened.

In a study published in PLOS One, researchers say SU 259, who was aged between 14 and 16 when he died, had a "considerably increased" cranial length. The image (below) shows how the skull has a "strongly inclined frontal bone with significant thickening" at the back. They believe he was subjected to a "tabular oblique type of ACD." This generally involved compressing the front and back of the skull using "hard and rigid tools."

Image showing one of the skulls discovered at the burial pit. Scientist say this boy's skull would have been altered with hard, rigid tools. PLOS One

"In the case from Osijek, the modification was likely performed using a rigid tool in the frontal region only, as no traces of flattening are present on the occipital bone," they said.

SU 750, who was 12 to 14 at the time of death, was found to have been subjected to a different type of ACD. In his case (pictured below), the skull had been flattened at the front, which had resulted in "a remarkable growth in cranium height." The team say this shape was likely achieved with "flexible tools such as bandages, bands, tapes, and/or headdress."

The second skull had been bandaged to be flatter and higher. Researchers believe the different shapes denote a visual marker of the individual's culture. M Kavka

After analyzing the skulls, the researchers look at the skeletons to understand more about the individuals' lifestyles and where they came from. The findings revealed all three were from different parts of the world. SU 259 was found to have ancestry related to East Asian populations, while SU 750 came from a culture more closely related to continental European populations. The third boy, whose skull was not altered, came from either Southern Europe or North Africa.

"It is important that the three individuals are from totally different parts of the world...since it implies mixing of tribes during this period," Pinhasi told Newsweek. "We did not anticipate to have actual first-generation migrants—or else they will appear so genetically different—from East Asia and the Middle East together in one pit with a local person."

Pinhasi and Kovak believe the different skull shapes found indicates ACD was used as a visual indicator to show association with different cultural groups. "So, in this case we probably have a Hun with an elongated head, maybe an Alan [nomadic Iranian tribe) with a skull with increased cranium height, and probably a member of some Germanic tribe [Ostrogoth or Gepid] with a normal-shaped head," Kovak said.

Researchers also found all three boys had suffered malnutrition during childhood: "These stressful episodes left visible markers on their teeth and bones," Kovak said, adding that while they cannot say this was the cause of death, it may have played a role. "Probably, due to malnutrition, their immune system was compromised, which had a negative impact on their health. We cannot say if they died of starvation, but it is a possibility."

Pinhasi added: "They shared a similar diet and possibly lifestyle and were buried in one pit. It means that there is a lot to unravel about the extent of movements and interactions of different tribes during this period. We still do not know that actual context of this pit so why were these three boys of a similar age but different genetic ancestry buried in one pit."

The scientists now hope to analyze additional deformed skulls to build a picture of the complex relationships being built at this turbulent time of mass migration. "This will lead to better understanding of social interactions during this period, which is in many respects marking the formation of modern European nations," Pinhasi said.